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514094f9 | 1 | <?xml version='1.0'?> |
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2 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" |
3 | "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> | |
0307f791 | 4 | <!-- SPDX-License-Identifier: LGPL-2.1+ --> |
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5 | |
6 | <refentry id="systemd-coredump" conditional='ENABLE_COREDUMP' | |
7 | xmlns:xi="http://www.w3.org/2001/XInclude"> | |
8 | ||
9 | <refentryinfo> | |
10 | <title>systemd-coredump</title> | |
11 | <productname>systemd</productname> | |
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12 | </refentryinfo> |
13 | ||
14 | <refmeta> | |
15 | <refentrytitle>systemd-coredump</refentrytitle> | |
16 | <manvolnum>8</manvolnum> | |
17 | </refmeta> | |
18 | ||
19 | <refnamediv> | |
20 | <refname>systemd-coredump</refname> | |
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21 | <refname>systemd-coredump.socket</refname> |
22 | <refname>systemd-coredump@.service</refname> | |
246ba4aa | 23 | <refpurpose>Acquire, save and process core dumps</refpurpose> |
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24 | </refnamediv> |
25 | ||
26 | <refsynopsisdiv> | |
12b42c76 | 27 | <para><filename>/usr/lib/systemd/systemd-coredump</filename></para> |
f6940bc3 | 28 | <para><filename>/usr/lib/systemd/systemd-coredump</filename> <option>--backtrace</option></para> |
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29 | <para><filename>systemd-coredump@.service</filename></para> |
30 | <para><filename>systemd-coredump.socket</filename></para> | |
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31 | </refsynopsisdiv> |
32 | ||
33 | <refsect1> | |
34 | <title>Description</title> | |
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35 | <para><filename>systemd-coredump@.service</filename> is a system service that can acquire core |
36 | dumps from the kernel and handle them in various ways. The <command>systemd-coredump</command> | |
37 | executable does the actual work. It is invoked twice: once as the handler by the kernel, and the | |
38 | second time in the <filename>systemd-coredump@.service</filename> to actually write the data to | |
39 | the journal.</para> | |
40 | ||
41 | <para>When the kernel invokes <command>systemd-coredump</command> to handle a core dump, it runs | |
42 | in privileged mode, and will connect to the socket created by the | |
43 | <filename>systemd-coredump.socket</filename> unit, which in turn will spawn an unprivileged | |
44 | <filename>systemd-coredump@.service</filename> instance to process the core dump. Hence | |
45 | <filename>systemd-coredump.socket</filename> and <filename>systemd-coredump@.service</filename> | |
46 | are helper units which do the actual processing of core dumps and are subject to normal service | |
47 | management.</para> | |
5146e7e8 | 48 | |
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49 | <para>Core dumps can be written to the journal or saved as a file. Once saved they can be retrieved |
50 | for further processing, for example in | |
51 | <citerefentry project='man-pages'><refentrytitle>gdb</refentrytitle><manvolnum>1</manvolnum></citerefentry>. | |
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52 | </para> |
53 | ||
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54 | <para>By default, <command>systemd-coredump</command> will log the core dump including a backtrace |
55 | if possible to the journal and store the core dump itself in an external file in | |
56 | <filename>/var/lib/systemd/coredump</filename>.</para> | |
5146e7e8 | 57 | |
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58 | <para>The behavior of a specific program upon reception of a signal is governed by a few |
59 | factors which are described in detail in | |
60 | <citerefentry project='man-pages'><refentrytitle>core</refentrytitle><manvolnum>5</manvolnum></citerefentry>. | |
61 | In particular, the core dump will only be processed when the related resource limits are sufficient. | |
f3962329 | 62 | </para> |
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63 | |
64 | <para>It is also possible to invoke <command>systemd-coredump</command> with | |
65 | <option>--backtrace</option> option. In this case, <command>systemd-coredump</command> expects | |
66 | a journal entry in the journal | |
28a0ad81 | 67 | <ulink url="https://www.freedesktop.org/wiki/Software/systemd/export">Journal Export Format</ulink> |
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68 | on standard input. The entry should contain a <varname>MESSAGE=</varname> field and any additional |
69 | metadata fields the caller deems reasonable. <command>systemd-coredump</command> will append | |
70 | additional metadata fields in the same way it does for core dumps received from the kernel. In | |
71 | this mode, no core dump is stored in the journal.</para> | |
246ba4aa | 72 | </refsect1> |
7382a3cc | 73 | |
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74 | <refsect1> |
75 | <title>Configuration</title> | |
76 | <para>For programs started by <command>systemd</command> process resource limits can be set by directive | |
77 | <varname>LimitCore=</varname>, see | |
78 | <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>. | |
79 | </para> | |
80 | ||
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81 | <para>In order to be used by the kernel to handle core dumps, |
82 | <command>systemd-coredump</command> must be configured in | |
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83 | <citerefentry project='man-pages'><refentrytitle>sysctl</refentrytitle><manvolnum>8</manvolnum></citerefentry> |
84 | parameter <varname>kernel.core_pattern</varname>. The syntax of this parameter is explained in | |
85 | <citerefentry project='man-pages'><refentrytitle>core</refentrytitle><manvolnum>5</manvolnum></citerefentry>. | |
f95b0be7 | 86 | systemd installs the file <filename>/usr/lib/sysctl.d/50-coredump.conf</filename> which configures |
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87 | <varname>kernel.core_pattern</varname> accordingly. This file may be masked or overridden to use a different |
88 | setting following normal | |
89 | <citerefentry><refentrytitle>sysctl.d</refentrytitle><manvolnum>5</manvolnum></citerefentry> | |
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90 | rules. If the sysctl configuration is modified, it must be updated in the kernel before it |
91 | takes effect, see | |
246ba4aa | 92 | <citerefentry project='man-pages'><refentrytitle>sysctl</refentrytitle><manvolnum>8</manvolnum></citerefentry> |
7382a3cc | 93 | and |
246ba4aa | 94 | <citerefentry><refentrytitle>systemd-sysctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>. |
7382a3cc | 95 | </para> |
246ba4aa | 96 | |
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97 | <para>In order to by used in the <option>--backtrace</option> mode, an appropriate backtrace |
98 | handler must be installed on the sender side. For example, in case of | |
98e9d710 | 99 | <citerefentry project='die-net'><refentrytitle>python</refentrytitle><manvolnum>1</manvolnum></citerefentry>, this |
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100 | means a <varname>sys.excepthook</varname> must installed, see |
101 | <ulink url="https://github.com/keszybz/systemd-coredump-python">systemd-coredump-python</ulink>. | |
102 | </para> | |
103 | ||
2dd67817 | 104 | <para>The behavior of <command>systemd-coredump</command> itself is configured through the configuration file |
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105 | <filename>/etc/systemd/coredump.conf</filename> and corresponding snippets |
106 | <filename>/etc/systemd/coredump.conf.d/*.conf</filename>, see | |
107 | <citerefentry><refentrytitle>coredump.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>. A new | |
108 | instance of <command>systemd-coredump</command> is invoked upon receiving every core dump. Therefore, changes | |
109 | in these files will take effect the next time a core dump is received.</para> | |
110 | ||
111 | <para>Resources used by core dump files are restricted in two ways. Parameters like maximum size of acquired | |
112 | core dumps and files can be set in files <filename>/etc/systemd/coredump.conf</filename> and snippets mentioned | |
113 | above. In addition the storage time of core dump files is restricted by <command>systemd-tmpfiles</command>, | |
114 | corresponding settings are by default in <filename>/usr/lib/tmpfiles.d/systemd.conf</filename>.</para> | |
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115 | |
116 | <refsect2> | |
117 | <title>Disabling coredump processing</title> | |
118 | ||
119 | <para>To disable potentially resource-intensive processing by <command>systemd-coredump</command>, | |
120 | set <programlisting>Storage=none | |
121 | ProcessSizeMax=0</programlisting> in | |
122 | <citerefentry><refentrytitle>coredump.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>. | |
123 | </para> | |
124 | </refsect2> | |
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125 | </refsect1> |
126 | ||
127 | <refsect1> | |
128 | <title>Usage</title> | |
129 | <para>Data stored in the journal can be viewed with | |
130 | <citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry> | |
131 | as usual. | |
132 | <citerefentry><refentrytitle>coredumpctl</refentrytitle><manvolnum>1</manvolnum></citerefentry> | |
133 | can be used to retrieve saved core dumps independent of their location, to display information and to process | |
134 | them e.g. by passing to the GNU debugger (gdb).</para> | |
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135 | </refsect1> |
136 | ||
137 | <refsect1> | |
138 | <title>See Also</title> | |
139 | <para> | |
140 | <citerefentry><refentrytitle>coredump.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
141 | <citerefentry><refentrytitle>coredumpctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
142 | <citerefentry><refentrytitle>systemd-journald.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>, | |
246ba4aa | 143 | <citerefentry><refentrytitle>systemd-tmpfiles</refentrytitle><manvolnum>8</manvolnum></citerefentry>, |
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144 | <citerefentry project='man-pages'><refentrytitle>core</refentrytitle><manvolnum>5</manvolnum></citerefentry>, |
145 | <citerefentry><refentrytitle>sysctl.d</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
146 | <citerefentry><refentrytitle>systemd-sysctl.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>. | |
147 | </para> | |
148 | </refsect1> | |
149 | </refentry> |